Hydrotreating of petroleum feedstocks and various boiling fractions thereof has become increasingly important because of more stringent product quality requirements. Furthermore, the petroleum industry foresees the time when it will have to turn to relatively high boiling feeds derived from such materials as coal, tar sands, oil-shale, and heavy crudes. Feeds derived from such materials generally contain significantly more deleterious components, such as sulfur, nitrogen, oxygen, halides, and metals. Consequently, such feeds require a considerable amount of upgrading in order to reduce the content of such components, thereby making them more suitable for further processing, such as fluid catalytic cracking and/or cracking and/or catalytic reforming.
Hydrotreating is well known in the art and usually requires treating a hydrocarbonaceous feed with hydrogen in the presence of a catalyst to effect conversion of at least a portion of the feed to lower boiling products, usually with removal of deleterious components. See for example U.S. Pat. No. 2,914,462 which discloses the use of molybdenum sulfide for hydrodesulfurizing gas oil and U.S. Pat. No. 3,148,135 which discloses the use of molybdenum sulfide for hydrorefining sulfur and nitrogen-containing hydrocarbon oils. Further, U.S. Pat. No. 2,715,603 discloses the use of molybdenum sulfide as a catalyst for the hydrogenation of heavy oils, and U.S. Pat. No. 3,074,783 discloses the use of molybdenum sulfides for producing sulfur-free hydrogen and carbon dioxide, wherein the molybdenum sulfide converts carbonyl sulfide to hydrogen sulfide. Molybdenum and tungsten sulfides have other uses as catalysts, including hydrogenation, methanation, water gas shift, etc. reactions.
In general, with molybdenum and other transition metal sulfide catalysts, as well as with other types of catalysts, greater catalyst surface areas generally result in more active catalysts than similar catalysts with lower surface areas. Thus, those skilled in the art are constantly trying to achieve catalysts having ever greater surface areas. More recently, it has been disclosed in U.S. Pat. Nos. 4,243,553 and 4,243,554 that molybdenum sulfide catalysts of relatively high surface area may be obtained by thermally decomposing selected thiomolybdate salts at temperatures ranging from about 3000.degree. to 8000.degree. C. in the presence of essentially inert, oxygen-free atmospheres. Suitable atmospheres are disclosed as consisting of argon, a vacuum, nitrogen, and hydrogen. In U.S. Pat. No. 4,243,554, an ammonium thiomolybdate salt is decomposed at a rate in excess of 15.degree. C. per minute, whereas in U.S. Pat. 4,243,553, a substituted ammonium thiomolybdate salt is thermally decomposed at a substantially slower heating rate of about 0.5.degree. to 20.degree. C. per minute. The processes disclosed in these patents are claimed to produce molybdenum disulfide catalysts having superior properties for water gas shift and methanation reactions as well as for catalyzed hydrogenation and hydrotreating reactions.
Hydrotreating catalysts comprising molybdenum sulfide, in combination with other metal sulfides, are also known. For example, U.S. Pat. No. 2,891,003 discloses an iron-chromium composition for desulfurizing olefinic gasoline fractions. Further, U.S. Pat. No. 3,116,234 discloses Cr-Mo and also Mo with Fe and/or Cr, and/or Ni for hydrodesulfurization. Also, U.S. Pat. No. 3,265,615 discloses Cr-Mo for hydrodenitrogenation and hydrodesulfurization.
Hydrotreating catalysts containing platinum are also known. For example, U.S. Pat. No. 3,422,002 discloses hydrotreating with a catalyst consisting essentially of 0.05 to 5 wt. % of a platinum series metal and about 4 to 30 wt. % of molybdena on alumina, the catalyst having been presulfided.
While various of these catalysts have met with commercial success, there still exists a need in the art for catalysts having ever improved properties with respect to hydrodenitrogenation over those conventionally used.